(1) Field of the Invention
The present invention is directed to an improved pipe freezing apparatus for use in freezing a plug of liquid within a pipe to facilitate repair or replacement of a pipe section, and in particular to a pipe freezing apparatus that is readily adaptable for use with pipes of different diameters.
(2) Description of the Prior Art
Repairing or replacing sections of fluid carrying pipe historically required draining of the pipe, and then cutting and replacing the pipe section. This time consuming and expensive procedure has been largely replaced through the use of pipe freezing devices that freeze a plug of liquid inside the pipe upstream of the pipe section that is to be repaired or replaced. The frozen plug prevents liquid from flowing from the pipe during repair. After the repairs have been made, the plug is allowed to thaw so that liquid can again flow through the pipe.
Pipe freezing devices are comprised of a refrigerant chamber that is placed around or against the pipe section to be frozen. In one type of device, the chamber includes a concave wall section having a radius that corresponds to the radius of the pipe. When used, the chamber, which is of a temperature conductive material such as aluminum, is placed against the pipe.
In another type of freezing device, referred to herein as a pipe enclosure device, the chamber is comprised of two sections that are clamped together around the pipe. The resultant chamber has openings in each end with a cross-section corresponding to the cross-section of the pipe. The present invention relates generally to a pipe freezing apparatus of this type.
The freezing device also includes an inlet that can be connected to a source of a low-temperature liquid refrigerant, e.g., liquid CO2 or nitrogen. The chamber also includes one or more exhaust ports, to which may be coupled a vent stack, normally on the opposite side of the chamber from the refrigerant inlet.
In use, the chamber is clamped around the pipe section with the pipe extending through the openings in the chamber. Refrigerant is then introduced, normally via a hose from a refrigerant source, into the chamber and allowed to evaporate, with the evaporated refrigerant escaping through one or more of the exhaust ports. As the refrigerant evaporates, heat is extracted from the pipe and fluid within the section of pipe enclosed by the chamber, resulting in freezing of the liquid within the section of pipe enclosed by the chamber.
The above pipe enclosure device is very effective in quickly freezing a plug of liquid within a pipe of a given diameter. However, pipes of different diameters are used in environments where there is a need to repair or replace a section of pipe. Therefore, it is often necessary for the repair person to carry pipe freezing devices with chambers having pipe openings sized for several different size pipes. As a result, the equipment is difficult to transport and costly.
There have been attempts to address the problem by using semi-circular chamber inserts that are fitted into radial slots in the chamber walls adjacent the chamber openings. However, these inserts are cumbersome, often falling out when placing the chamber sections around a pipe. Therefore, there is a need for a single pipe freezing chamber of the pipe enclosure type that can fit around pipes of different sizes without leakage of refrigerant from between the pipe outer wall and the chamber wall.